Following mukul's answer, I specifically recommend you check out SSDLite-MobileNetV2.
It's a lite-weight model, which is still enough expressive for good results.
Especially when you're restricting yourself to a single class, as you can see in the example of FaceSSD-MobileNetV2 as in here (Note however this is vanilla SSD).
So you can simply Take the pre-trained model of SSDLite-MobileNetV2 with the corresponding config file, and modify it for a single class.
This means changing num_classes to 1, modifying the label_map.pbtxt, and of course - preparing the dataset with the single class you want.
If you want a more robust model, but which has no pre-trained mode, you can use an FPN version.
Checkout this config file, which is with MobileNetV1, and modify it for your needs (e.g. switching to MobileNetV2, switching to use_depthwise, etc).
On one hand, there's no detection pre-trained model, but on the other the detection head is shared over all (relevant) scales, so it's somewhat easier to train.
So simply fine-tune it from the corresponding classification checkpoint from here.